Cord/rubber composites are often considered as homogeneous anisotropic media in macro-mechanical structural analysis. Challenges, however, are associated with significant non-linearity of their deformation and the visco-elastic nature of rubber matrix. These visco-elastic composites are often subjected to cyclic loading conditions (periodic excitations) and exhibit energy losses due to their hysteretic behavior. An approach is proposed to quantify these hysteretic energy losses under general case of two or three-dimensional cyclic loading. The approach provides a simple mathematical description of this non-linear visco-elastic phenomenon. Representative experimental data are considered to show the reliability of the approach. Uni-directionally reinforced single layer composites are considered under different off-axial cyclic loads to model 2-D stress/strain states. Possible methods are discussed to define composite properties using the proposed approach.
The interactions between polyiethylene terephthalate) (PET) and six high temperature solvents are discussed in terms of gelation and melting temperature depression. The six solvents are 1'-acetonaphthone (AN), phenyl ether (PE), biphenyl (BP), 1-methyl naphthalene (MN), nitrobenzene (NB), and a eutectic mixture of phenyl ether and biphenyl (EU). Although the six solvents have very similar solubility parameter values, the dissolution, gelation, and gel melting temperatures of the PET-solvent systems are vastly different. The characteristic transition temperatures (dissolution, gelation, and gel melting temperatures) of the six solvents decrease in the following order: PE > EU > BP > MN > AN > NB, which is the reverse order of the solvent power. While the transition temperatures of the gel vary with the solvent system, the melting temperature of the dry gel formed from quiescent solution is independent of solvent system. That is, PETsolvent interactions are only discernible in solvated state (wet gel). All the experimental results suggest crystallization is the primary cause of gelation of high temperature PET solutions, with crystals acting as junction points in the network. Based on the dissolution and gel melting temperatures, interaction parameters for the six PET-solvent systems have been calculated.
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